Apple scab
Venturia inaequalis
Pathogen: Venturia inaequalis is a fungal pathogen responsible for causing apple scab, a common and damaging disease affecting apple trees (Malus domestica).
Symptoms:
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Leaf Lesions:
- Olive Green to Dark Brown Spots: Circular to irregularly shaped lesions on leaves with colors ranging from olive green to dark brown.
- Velvety Appearance: Lesions may have a velvety or scaly appearance.
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Fruit Lesions:
- Scab-Like Spots: Similar lesions may appear on the surface of apples, resembling scabs.
- Distorted and Cracked Fruits: Severely infected fruits may become distorted, cracked, and unmarketable.
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Twig and Fruit Stem Lesions:
- Lesions on Twigs and Fruit Stems: Twigs and fruit stems can also develop scab-like lesions.
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Reduced Photosynthesis:
- Premature Leaf Drop: Severe infections can lead to premature leaf drop, affecting the tree's ability to photosynthesize.
Identification:
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Leaf Lesions:
- Circular to irregular lesions with an olive green to dark brown color.
- Velvety or scaly appearance on the lesions.
-
Fruit Lesions:
- Scab-like spots on the surface of apples.
- Distorted and cracked fruits in severe cases.
Conditions Favoring Disease:
- Humid Conditions: Apple scab thrives in humid environments.
- Rain or Moisture: Moisture on leaves and fruit from rain or irrigation facilitates spore dispersal and infection.
Management:
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Resistant Varieties:
- Plant Resistant Cultivars: Choose apple varieties that exhibit resistance or tolerance to Venturia inaequalis.
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Cultural Practices:
- Leaf Removal: Remove and destroy infected leaves to reduce inoculum.
- Proper Pruning: Prune trees to improve air circulation and reduce humidity within the canopy.
- Sanitation: Remove and destroy fallen leaves to minimize overwintering spores.
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Fungicides:
- Protective Fungicides: Regular application of fungicides during the growing season, especially during periods conducive to disease development.
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Post-Harvest Practices:
- Proper Storage: Store harvested apples in cool and dry conditions to minimize the development of scab lesions.
Note: Integrated disease management, combining cultural practices, resistant varieties, and fungicides, is often the most effective approach.




























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